Facing materials for an internal combustion engine cylinder and a cooperating piston ring

ABSTRACT

Abrasion wear of piston rings and of the inner cylinder wall of an internal combustion engine is very low when the piston ring consists of cast iron of specified composition and a Rockwell hardness of at least C 40, and the cylinder wall consists of electrodeposited nickel having fine particles of silicon carbide or other very hard material dispersed therein so that the cylinder wall has a hardness of Rockwell A 70 - A 100.

United States Patent [1 1 Mori et al.

[54] FACING MATERIALS FOR AN INTERNAL COMBUSTION ENGINE CYLINDER AND ACOOPERATING PISTON RING Inventors: Yoshio Mori, Tokyg yoshihltp sato,Kawaguchi; Kentaro Takahashi, Omiya, all of Japan Nippon Piston RingKaisha, Tokyo, Japan Filed: Dec. 1, 1971 Appl. No.: 203,877

[73] Assignee: Kabushika [30] Foreign Application Priority Data Dec. 12,1970 Japan ..4s 110109 US. Cl. ..277/235 R, 123/193 CP, 277/96, 308/4,418/179 Int. Cl. ..F16j 9/12, F16j 15/08 Field of Search ..277/235 B,236, 216, 277/96, 237; 204/9; 418/179; 92/169, 222,

67, 84; 308/4; 123/193 C, 193 P, 193 CP References Cited UNITED STATESPATENTS 1,449,615 McLeod ..277/216 3,464,707 9/1969 Packard et al..277/235 3,658,451 4/1972 Gomada ..277/236 3,199,929 8/1965 McLean etal. ..308/4 "FOREIGN PATENTS on APAPLICYATIONSV 409,579 5/1934 GreatBritain ..277/236 Primary Examiner-Joseph R. Leclair AssistantExaminerRobert I. Smith Attorney-Kurt Kelman et al.

[57] ABSTRACT 7 Claims, No Drawings FACING MATERIALS FOR AN INTERNALCOMBUSTION ENGINE CYLINDER AND A COOPERATING PISTON RING This inventionrelates to a combination of materials in the face portions of twomembers of an apparatus which frictionally engage each other and aremoved relative to each other in area contact, and particularly to facingmaterials for the inner cylinder wall of an internal combustion engineand for a piston ring reciprocated in the cylinder during engineoperation.

With a trend toward increasing rotary speed and higher compression ratioin internal combustion engines, particularly gasoline engines forautomotive vehicles, the wear resistance of piston rings and of theinner cylinder walls frictionally engaging the rings must be improved iflong periods of operation between overhauls are desired. It has beencommon practice to electrodeposit chromium on one of the frictionallyengaged face portions for reducing wear, but the improvement achievedthereby is limited so as not to be satisfactory under severe operatingconditions.

It has now been found that a certain combination of materials for theface portions of an inner cylinder wall or cylinder liner and of apiston ring frictionally engaging the wall while being reciprocated bythe piston in the cylinder suffers significantly less abrasive wear thanthe best combinations practically available heretofore.

According to the invention, one of the frictionally engaged faceportions essentially consists of cast iron having a hardness of at least40 on the Rockwell C scale and a particulate graphite content of 0.5 to3 percent by weight in a martensite matrix, to 45 percent of the area ofa polished section of the cast iron consisting of c'ementite.

The other face portion essentially consists of electrolyticallydeposited nickel and pulverulent particles of a material much harderthan the nickel and dispersed in the same.

The cast iron according to the invention has the following chemicalcomposition, in percent by weight:

Mn 0.3 1.5 Impurities including S 0.1 max.

P abt. 0.1 max.

Fe Balance At a carbon content of less than 2.5 percent, an adequateamount of particulate graphite is not formed in the microstructure. At acarbon content higher than 4.0 percent, a stable carbide deposit cannotbe expected. The required graphite content is not readily achieved withless than 1.5% Si, and the desired stable carbide phase is not readilyformed with more than 3.0 percent silicon.

At least 0.1 percent molybdenum is needed for achieving the requiredhigh hardness, and at least 0.1 percent nickel for adequate strength.The cost of the cast iron becomes excessive with a molybdenum or nickelcontent of more than 1.0 percent.

A minimum of 0.1 percent chromium is needed for adequate carbideformation, and more than 1.0 percent chromium interferes with graphiteformation. At least 0.5 percent graphite is needed as a solid lubricant,but

more than 3.0 percent graphite makes the cast iron brittle.

The abrasion resistance of the cast iron is insufficient when the areapercentage of the carbide (cementite) in a polished section is lowerthan 10 percent, and it is almost impossible to obtain a carbide area ofmore than 45 percent under the other conditions specified.

A minimum of 0.3 percent manganese is needed to hold the sulfur contentwithin the necessary limits, while more manganese increases the carbidearea to more than 45 percent in an undesirable manner. Incidentalimpurities, particularly sulfur and phosphorus, must be limited toprevent brittleness.

The desired and necessary hardness of the cast iron is achieved bychilling the liquid alloy in a mold at 1450C and by thereafter holdingit at l0O0C for 2 hours to graphitize enough carbide. These conditionsare readily met in casting a piston ring, and may be modified in a knownmanner when it is desired to make the cylinder or cylinder liner of castiron.

The other face portion is prepared in the manner described in Grazen US.Pat. No. 3,061,525, issued Oct. 30, 1962. Nickel is electrodeposited ona base of cast iron or other suitable conductive material, and fineparticles of greater hardness are entrapped in the electrodeposit onwhich they may settle by gravity from the agitated electrolyte. Suitablehard substances known to be capable of being embedded in a nickel plateinclude oxides of aluminum or iron, carbides of silicon or tungsten, anddiamond, but also finely dispersed hard metals such as tungsten, andmixtures of these materials. The amount of embedded hard particles maybe controlled in a known manner by varying the agitation of theelectrolyte, the particle size, the current density, and other processvariables, as partly discussed in the afore-mentioned patent, and ingreater detail in a more recent paper by Ruml [Metalloberflaeche 23(1969) 2, 35-36]. The process is readily controlled to make the hardnessof the reinforced nickel deposit on the Rockwell A scale.

The composition of the electrolyte is not critical, but

the following range of ingredients has been found to be controlledconveniently:

NiSO..7H,O I50 300 grams/liter NiCll,.6H,0 30 70 grams/liter H 80, 20 40grams/liter Silicon carbide, among the hard materials mentioned above,combines high hardness with low cost in a most desirable manner at thistime and is the preferred pulverulent material held dispersed in theelectrolyte by agitation in amounts of 10 to 100 g per liter at aparticle size of 10 to 100 microns. The pH value of the electrolyte ischosen according to other process variables between 1 and 7 in aconventional manner. The temperature may be between ambient temperatureand 70C, and the current density between 10 and 100 amps./sq.ft.Electrolytic nickel is the preferred anode material.

The following example is further illustrative of this invention and ofthe results achieved thereby EXAMPLE Piston rings having dimensions of74 X 1.5 X 3.4 mm were made of cast iron according to the inventionconsisting of C3.l2%, Si 2.05%, Mo 0.73%, Ni 0.55%, Cr 0.54%, Mn 0.68%,P 0.11%, S 0.05%, Fe balance, and having a Rockwell hardness of C 55.

For comparison purposes, piston rings of the same dimensions were madeof conventional cast iron consisting of C 3.55%, Si 2.42%, Mn 0.70%, P0.15%, S 0.08%, Fe balance, Rockwell B 98, and their circumferences werechromium plated to a thickness of 0.12

An air-cooled gasoline engine having a total displacement of 1298 cm anddeveloping 100 hp at 7200 rpm. was equipped with four cylinders of castiron containing C 3.24%, Si 2.15%, Mn 0.57%, P 0.22%, S 0.07%, balanceiron, having an effective bore of 74 mm and with pistons having a strokeof 75.5 mm and a maximum velocity of 18.1 m/sec.

Two of the cylinders were internally coated cathodically to the desiredbore size from an electrolyte containing NiSO,.7H,O 235 g/literNiCl,.6l-l,0 54 g/liter H 80 28 g/liter SiC (30 y.) 30 g/liter withsufficient agitation to keep the SiC particles almost completely insuspension at pH 5.8, 51.5C, and 30 amps./sq.ft. for 30 minutes. Thecoating so produced had a thickness of 0.05 mm and a Rockwell hardnessofC 62 (corresponding to A 82).

The piston rings of the invention were installed on the pistonsreciprocating in the coated cylinders, whereas the chromium-plated ringswere installed in the bare cast-iron cylinders. The engine was thenoperated continuously for an extended period.

The abrasion loss per 100 hours of engine operation was 5 microns on theconventionally surfaced cylinders, and 2 microns on the coated cylindersof the invention. It was microns on the chromium plated piston rings and5 microns on the uncoated cast iron rings of the invention. Analogousreductions in abrasion loss were observed at maximum piston speeds of 25m/sec. and contact pressures of 100 kg/cm.

While the invention has been described with reference to a piston ringof hard cast iron cooperating with an internally nickel-plated cylinder,the materials of the face portions of the ring and cylinder may beinterchanged in an obvious manner without substantial loss in wearresistance, and the invention is generally applicable to any pair ofmembers having frictionally engaged face portions and moved relative toeach other in area contact during normal operation of an apparatus,particularly where the speed of movement and the contact pressure arehigh.

It should be understood, therefore, that the foregoing disclosurerelates only to a preferred embodiment of the invention, and that it isintended to cover all changes and modifications of the example of theinvention herein chosen for the purpose of the disclosure which do notconstitute departures from the spirit and scope of the appended claims.

What is claimed is: 1. In an apparatus including two members havingrespective first and second face portions frictionally engaging eachother, and means for moving the frictionally engaged face portionsrelative to each other in area contact, the improvement which comprises:

1. said first face portion essentially consisting of cast iron having ahardness of at least 40 on the Rockwell C scale, and a particulategraphite content of 0.5 to 3 percent by weight in a martensite matrix,10 to 45 percent of the area of a polished section of said cast ironconsisting of cementite; and

2. said second face portion essentially consisting of electrolyticallydeposited nickel and pulverulent particles of a material much harderthan said nickel dispersed in the same.

2. In an apparatus as set forth in claim 1, one of said members being apiston ring in an internal combustion engine, and the other memberconstituting the inner wall of a cylinder receiving said piston ringtherein.

3. In an apparatus as set forth in claim 2, said cast iron containing2.5 4.0 percent carbon, 1.5 3.0 percent silicon, 0.1 1.0 percentmolybdenum, 0.1 1.0 percent nickel, 0.1 1.0 percent chromium, 0.3 1.5percent manganese, incidental impurities, the balance being iron, saidimpurities including not substantially more than 0.1 percent phosphorusnor more than 0.1 percent sulfur.

4. in an apparatus as set forth in claim 3, said material being an oxideof aluminum or iron, a carbide of silicon or tungsten or diamond.

5. In an apparatus as set forth in claim 4, the amount of said materialin said second face portion being sufficient to make the hardness ofsaid second face portion on the Rockwell A scale.

6. In an apparatus as set forth in claim 5, the size of said particlesbeing between 10 and 100 microns.

7. In an apparatus as set forth in claim 3, said first face portionbeing the face portion of said piston ring, and said material beingsilicon carbide.

2. said second face portion essentially consisting of electrolyticallydeposited nickel and pulverulent particles of a material much harderthan said nickel dispersed in the same.
 2. In an apparatus as set forthin claim 1, one of said members being a piston ring in an internalcombustion engine, and the other member constitutIng the inner wall of acylinder receiving said piston ring therein.
 3. In an apparatus as setforth in claim 2, said cast iron containing 2.5 - 4.0 percent carbon,1.5 - 3.0 percent silicon, 0.1 - 1.0 percent molybdenum, 0.1 - 1.0percent nickel, 0.1 - 1.0 percent chromium, 0.3 - 1.5 percent manganese,incidental impurities, the balance being iron, said impurities includingnot substantially more than 0.1 percent phosphorus nor more than 0.1percent sulfur.
 4. In an apparatus as set forth in claim 3, saidmaterial being an oxide of aluminum or iron, a carbide of silicon ortungsten or diamond.
 5. In an apparatus as set forth in claim 4, theamount of said material in said second face portion being sufficient tomake the hardness of said second face portion 70 - 100 on the Rockwell Ascale.
 6. In an apparatus as set forth in claim 5, the size of saidparticles being between 10 and 100 microns.
 7. In an apparatus as setforth in claim 3, said first face portion being the face portion of saidpiston ring, and said material being silicon carbide.